Ab Initio calculations relevant to the mechanism of chemical carcinogenesis II: The nitrous acidium ion—a powerful nitrosating agent

In our attempts to determine the structure of the nitrous acidium ion we have calculated the structure of various isomers of protonated nitrous acid using an ab initio SCF (selfconsistent field) approach with an extended basis set. The most stable isomer is found to be ON(H₂0)⁺; however, hydration of NO⁺ by three or more molecules of water results in the formation of H₃O⁺ and the regeneration of nitrous acid. The nitrous acidium ion is thus found to be a transient species.